Wireless Bidirectional Relaying and Latin Squares

The design of modulation schemes for the physical layer network-coded two way relaying scenario is considered with the protocol which employs two phases: Multiple Access (MA) Phase and BroadCast (BC) Phase. It was observed by Koike-Akino et al. that adaptively changing the network coding map used at the relay according to the channel conditions greatly reduces the impact of multiple access interference which occurs at the relay during the MA Phase and all these network coding maps should satisfy a requirement called the exclusive law. The authors highlight the issues associated with the scheme proposed by Koike-Akino et al. and propose a scheme which solves these issues.